BAGHDAD — In a mansion tiled with salmon-pink marble, Sunni politician Osama al-Nujaifi greets visitors in an expansive meeting room. From a chair flanked by the national flag, he insists he is still vice president of Iraq — even though Iraq’s prime minister says he is not.

Nujaifi’s position and Iraq’s two other vice presidencies were eliminated by Prime Minister Haider al-Abadi in purported cost-cutting measures announced this summer. But there is little change at Nujaifi’s office. His staff is still paid, he said, and he is working as normal.

Nujaifi’s defiance highlights Abadi’s weak hand as he fails to execute anything but superficial changes after pledging wide-ranging reforms in response to street protests. Smelling blood as he flounders, his political rivals have turned on him, while ­Iranian-backed militias leverage what they can from him.

His precarious position appears likely to raise concerns in Washington as it backs him in his fight against the Islamic State — a war that has taken on a new urgency for the United States and Europe as the group has rapidly expanded its operations overseas.

“His position is shaking,” said Ali Adeeb, a senior member of Abadi’s Dawa party. “Everyone is talking about who Haider al-Abadi will be replaced by. Perhaps the will of the big people that want this change will succeed.”

Since his first days in office, Abadi has struggled to assert himself in the world of Iraqi politics as he has tried to balance the competing interests of Iraq’s two main security allies — Iran and the United States. His eroded position could shift that balance, allowing Iran to extend its reach into Iraqi politics and security matters.

It has been a challenge from the outset. After the ouster of his predecessor, Nouri al-Maliki, Abadi was not initially suggested as a successor, but he later emerged as a consensus candidate.

Maliki, who vehemently objected to being removed, remains the secretary general of the Dawa party. He is widely said to have worked to sabotage his rival since his ouster, splitting loyalties within the party.

“He’s in a hard position,” Sami al-Askari, a veteran Shiite politician, said of Abadi. “The party is not united behind him.”

Adeeb said Abadi is perceived to be “illegitimate.”

When protesters took to the streets demanding better services and action against corruption, Abadi, perhaps hoping to prove his mettle, promised the biggest shake-up in Iraqi politics since the 2003 U.S.-led invasion. He appeared emboldened by the support of demonstrators and of Iraq’s top Shiite cleric, Grand Ayatollah Ali Sistani.

In addition to axing the vice presidential posts — which included that of Maliki — Abadi merged four ministries and closed others.

But his reform attempts have backfired, delivering little while managing to irk powerful political players who stand to lose out. Proposed salary reforms turned street protesters against him.

Some of the few changes he made appear to have been unconstitutional, giving ample fodder to those who opposed change — and there are plenty of those in a country where many politicians line their pockets through rampant graft.

In a severe blow to the prime minister, Iraq’s parliament voted unanimously this month to withdraw support for his reform package, accusing him of overstepping his powers. During a recent visit to Shiite holy city of Najaf, he met with Shiite clerics but not Sistani. Although the grand ayatollah often steers clear of politics and politicians, that was widely viewed as a snub by Sistani, who had initially given Abadi political cover for his actions.

“We’d need a prophet to do real reforms in Iraq, not Abadi,” said Hadi al-Amiri, head of the Badr Organization, a Shiite political party with a powerful armed wing. “Basically, there are no reforms. All they’ve done is change a few names.”

But as Iraqi politicians attempt to leverage what they can out of the situation, it is Abadi’s weakness that may save him. There are few alternatives, and the United States and, for the moment, Iran are too concerned about a potential power vacuum to want to see him leave, analysts and politicians said.

“The probability is he will stay, but he’s got a big black eye,”said Kirk Sowell, a political risk analyst and the publisher of Inside Iraq Politics.

Iraqi militias, meanwhile, appear to be using the opportunity to get what they can. Last month, Abu Mahdi al-Muhandis, leader of the amalgamation of largely Shiite militias known as the popular mobilization units, wrote a patronizing letter to Abadi demanding more support for his fighters. In an embarrassment to the prime minister, it was leaked to the public.

“I have told you repeatedly that we need headquarters and training camps and weapons and munitions,” the letter said. “Why and why and why?” he wrote, questioning the supposed lack of support.

Amiri, who had just returned from a visit to Iran and is close to the leadership there, said it is not in Iran’s interest to remove Abadi now.

He stressed that Abadi must give more support to militia fighters in next year’s budget. But regardless, he said, the country should “stand by Abadi” because it is facing a real threat.

“Only a crazy man would want to be in his position right now,” Amiri said.